very year for the past few years, supporters of the global effort to wipe out polio have made an optimistic declaration: This could be the year that polio ends. And this year, the 30th anniversary of the launch of the ambitious program, was no exception.
But just three months into 2018, the projection is less rosy.
Eight cases of polio have already been reported, in Afghanistan and Pakistan, when there were only 22 cases in total. That’s three more than were seen over the same period last year. In addition, sewage surveillance in those two countries has turned up 28 other polioviruses so far this year — during what is supposed to be the low season for poliovirus transmission.
At least some leaders of the eradication campaign have already started making mental preparations for the possibility that 2018 may not be the year the world licks polio.
“We would like it to be the year, but the first few months of the year have not been all that positive,” acknowledged Michel Zaffran, director of polio eradication for the World Health Organization.
The frustrating effort to scrub polioviruses from the planet is like a nightmarish blend of whack-a-mole and Groundhog Day. It’s never clear what the next challenge will be, only that the chances are great that there will be one. And then another.
In 2016, there was news of polioviruses paralyzing children in Nigeria, which had gone two years without any cases. Last year Syria endured a large outbreak caused by the live (but weakened) viruses in the oral vaccine used in many countries. The vaccine viruses can regain the power to paralyze if they circulate among unvaccinated children — of which the war-ravaged country had many. At least 74 children were paralyzed in that outbreak.
Currently, the spread of polioviruses in Afghanistan and Pakistan has the Global Polio Eradication Initiative worried. For years the virus has moved back and forth between the two countries to the point where the polio program considers them one outbreak, and synchronizes the timing of vaccination campaigns between the two.
Seven of the cases so far this year have been in Afghanistan, the other in Pakistan. In the former, cases have occurred in two parts of the country — four in the south near Kandahar, and three in the northeast, near Jalalabad.
Zaffran is hopeful the spread in the south can be stopped, but is more concerned about the situation in the northeast, where getting vaccine to children can still be a challenge and where outsiders — whom the program would normally use to verify how well vaccination campaigns are running — cannot safely travel.
In the United States and most of the rest of the world, it’s been decades since spread of the virus was halted. At present, polio is endemic — its transmission has never been stopped — in only three countries, Afghanistan, Pakistan, and Nigeria.
The situation in Nigeria appears to be more hopeful, said Zaffran, who recently traveled there. Access to children in areas of insurrection poses challenges to the polio program there as well. But the number of children the campaign’s vaccinators can’t safely reach has been cut substantially since the 2016 outbreak, he said. While there were about 600,000 children in out-of-reach areas two years ago, that number is now around 100,000.
Nigeria reported no polio cases in 2017 and no viruses were found in sewage either. “It is getting increasingly plausible that we will be able to interrupt transmission [there] if it hasn’t yet been interrupted,” Zaffran said.
There are other positive notes. A global shortage of injectable polio vaccine — which does not carry the risk the oral vaccine does — has eased up to a degree. “I would say the situation will remain fragile through this year and probably into next year. And only in 2020 will we have more manufacturers on board and therefore a larger base of supply,” Zaffran said.
And though it’s still too early say for sure, it appears that a move to drop one component of the oral vaccine — the part that protected against type 2 polioviruses — has been successful.
When the WHO, the Centers for Disease Control and Prevention, UNICEF, and the service club Rotary International started the polio eradication campaign in 1988, there were three strains of polioviruses. (The Gates Foundation, which is also a partner in the Global Polio Eradication Initiative, joined later.)
Type 2 viruses haven’t been seen since 1999, and were declared eradicated in 2016. (Type 3 viruses are also thought to be gone but the formal process to declare eradication hasn’t yet been undertaken.)
The vaccines — oral and injectable — continued to protect against all three virus types. But over time it became apparent that the type 2 component in the oral vaccine was causing a problem. In places where there was vaccination coverage was low, the vaccine viruses would circulate among children and regain the power to paralyze.
In 2016 countries were told to stop using the three-strain oral vaccine, moving instead to a version that included protection against only type 1 and type 3 viruses. That coordinated move, which took place over a two-week period last spring, was called “the switch.”
The move had to be taken, polio experts realized. But they also knew that it was a risky step if type 2 vaccine viruses were circulating, leaving some children with no protection against those vaccine viruses. Initially the plan involved giving all kids at least a dose of the injectable vaccine in the leadup to the switch, so that they would have at least some protection against type 2 viruses. But some countries still haven’t been able to do that, because of the vaccine shortage.
Since the switch there have been two large outbreaks involving the type 2 vaccine viruses, in Syria and in the Democratic Republic of the Congo. But things appear to be looking up on this front, Zaffran said.
“I’m hopeful that we’re seeing the end of the type 2 occurrences in a significant manner and therefore we will soon be in a position to say: The switch was a major step forward,” he said. “But it’s still early time for that.”